This invention relates generally to a metering regulator. More specifically, but not by way of limitation, this invention relates to a compact metering regulator that can be installed in or attached to individual pneumatic tools for controlling the volume and pressure of air flowing to the motor of each pneumatic tool.
In the past, separate devices were required for metering or controlling the volume of air flowing to air tools and for regulating the pressure at which the tools stop. Pneumatic tools, such as nutrunners, generally operate on the principle that when the torque on the threaded fastener reaches a certain value, it will be reflected as a pressure in the tool and at some predetermined pressure, depending on the torque desired on the nut, the tool will stall and stop. This is generally accomplished by a pressure regulator which may be installed in the tool or separate therefrom. It is, of course, desirable to have the pressure regulator as accurate as possible to promote the consistent torque application to the threaded fasteners.
The volume of air flowing into the tool can also affect the torque applied to the threaded fastener. This occurs due to the kinetic energy being imparted to the threaded joint by a rapidly spinning motor due to with a high volume flow into the pneumatic tool.
Air flow control allows the free speed RPM of a tool to be reduced with a minimal reduction in stall torque. Air pressure control allows the stall torque of a tool to be reduced with a minimal reduction in free speed. Air pressure regulation is the preferred method for controlling torque on threaded joints with moderate variations in torque rates. Pressure control reduces torque scatter caused by varying air pressure. Air flow control can lower the torque spread between torque rates. Air flow restrictions can reduce motor speeds with minimal stall torque loss. This can significantly reduce the kinetic energy imparted to a threaded joint with a high torque rate and have little or no effect on a joint with a low torque rate.
Accordingly, it is desirable to b able to control both the pressure at stall, that is to regulate the pressure where the tool stops, as well as to be able to simultaneously control the volume of flow so that the tool will be operating at the optimum possible speed consistent with the ability to apply the desired torque. The combination of controls provides the best consistency of response to the desired torque.
An object of this invention is to provide a compact metering regulator which simultaneously provides both the control of the volume of air flowing into the motor and the control of the pressure at which the tool stalls or shuts off.